A wide variety of materials have been described for use as absorbent gelling materials in disposable absorbent articles. Such materials include natural-based materials such as agar, pectin, gums, carboxyalkyl starch and carboxyalkyl cellulose as well as synthetic materials such as polyacrylates, polyacrylamides and hydrolyzed polyacrylnitrile. While the natural-based absorbent gelling materials are known for use in such hygienic absorbent articles, they have not gained wide usage in such articles. The natural-based absorbent gelling materials have not gained wide usage in absorbent articles, at least in part, because their absorbent properties are generally inferior compared to synthetic absorbent gelling materials, such as the polyacrylates. Most of the commercially available disposable absorbent articles for body care like sanitary napkins and diapers comprise synthetic absorbent gelling materials, typically polyacrylates, to deliver body fluid absorption and retention characteristics. However although such synthetic absorbent gelling materials exhibit outstanding absorption capacity towards de-ionized water, their absorption capacity towards electrolytes/salts-containing solutions like menses is lower. It is generally believed that this effect results from the electrolyte content of body fluids and this effect is often referred to as ‘salt poisoning’.
The water absorption and water retention characteristics of synthetic absorbent gelling materials are due to the presence in the polymer structure of ionisable functional groups. These groups are usually carboxyl groups, a high proportion of which are in the salt form when the polymer is dry but which undergo dissociation and salvation upon contact with water. In the dissociated state, the polymer chain will have a series of functional groups attached to it which groups have the same electric charge (e.g., —COO− −OOC—) and thus repel one another. This leads to expansion of the polymer structure, which, in turn permits further absorption of water molecules although this expansion is subject to the constraints provided by the cross-links in the polymer structure, which must be sufficient to prevent dissolution of the polymer. It is assumed that the presence of a significant concentration of electrolytes in the water like in menses or urine or milk discharge interferes with the dissociation of the functional groups and leads to the ‘salt poisoning effect’. This salt poisoning effect is detrimental to the absorption capacity of the polymer.
It is thus a need to provide absorbent articles with improved absorption performance in the presence of electrolytes, for example in the case of menses or lactational fluid.
Whilst the primary focus of absorbent articles, in particular feminine hygienic absorbent articles like sanitary napkins, breast pads and pantiliners, remains the ability of these articles to absorb and retain fluids, another important area of development in this field is the control of odorous compounds contained within the absorbent articles during their use.
The presence and detection of malodorous compounds from absorbent articles during their use, particularly those associated with menstruation may cause the wearer of these articles embarrassment. Thus, the prevention of the detection of malodor from such articles is highly desirable too.
In use, the absorbent articles are known to acquire a variety of compounds, for example volatile fatty acids (e.g. isovaleric acid), ammonia, amines (e.g. triethylamine), sulphur containing compounds (e.g. mercaptans, sulphides), alcohols, ketones and aldehydes (e.g., furaldehyde) which release unpleasant odors. These compounds may be present in the bodily fluid or may be developed by chemical reactions and/or any fluid degradation mechanisms once the bodily fluid is absorbed into the absorbent article like for example a feminine hygienic absorbent article. In addition bodily fluids usually contain microorganisms and/or enzymes that can also generate malodorous by products as a result of degradation mechanisms like putrefactive degradation, acid degradation, proteins degradation, fat degradation and the like.
Various odor control materials have been disclosed in the art to combat some of the unpleasant odors referred to above. Indeed solutions have been provided that use different technical approaches like masking, i.e., covering the odor with a perfume, or absorbing the odor already present in the bodily fluids and those generated after degradation, or preventing the formation of the odor.
Most of the focus in the prior art is found on the odor absorption technology. Examples of these types of compounds include activated carbons, clays, zeolites, silicates, cyclodextrine, ion exchange resins and various mixture thereof as for example described in EP-A-348 978, EP-A-510 619, WO 91/12029, WO 91/11977, W089/02698, and/or WO 91/12030. All of these types of odor control agents are believed to control odor by mechanisms whereby the malodorous compounds and their precursors are physically absorbed by the agents and thereby hinder the exit of the odor from articles like absorbent articles. However, such mechanisms are not completely effective as the formation of the odor itself is not prevented and thus odor detection is not completely avoided.
Thus although these materials provide some control of odors associated with bodily fluids, there still exists a need of further improvement in terms of odor control of malodors which are generated by the human body, or from bodily fluids such as perspiration, urine, faeces, menstrual fluids, vaginal fluids, lactational fluid and the like.
More particularly, it is an object of the present invention to provide articles, especially disposable absorbent articles, which deliver a broader spectrum of odor control while delivering a high protection level. Actually it is an object of the present invention to provide articles, especially disposable absorbent articles, with improved odor control properties and improved fluid absorption performance especially in the presence of electrolytes-containing solutions for example in the case of menses or urine or lactational fluid.
It has now surprisingly been found that the combination of chitosan material together with an anionic absorbent gelling material in an article, like an absorbent article typically coming into contact with bodily fluid, delivers both improved odor control performance over a broad range of malodors compounds and improved absorption performance. Indeed this combination has been found to be particularly effective in the case of electrolytes-containing solutions like menses or urine or lactational fluid.
More particularly, it has surprisingly been found that the addition of an anionic absorbent gelling material on top of chitosan material results in a synergistic effect in terms of odor control. Indeed, this combination gives more odor reduction than the odor reduction associated with the use of one of these two classes of ingredients alone at the same total level (either chitosan material alone or the absorbent gelling material alone) in an absorbent article coming into contact with bodily fluids.
Actually the combination of chitosan material with an anionic absorbent gelling agent allows to combine odor control mechanisms by which the overall malodor detection is synergistically reduced or even prevented.
Without to be bound by any theory it is believed that chitosan material provides odor control of malodors components associated with bodily fluid by multiple mechanisms.
Firstly, the odor absorption and retention characteristics of chitosan materials are due to the presence in the polymer structure of ionisable cationic functional groups. These groups are usually ammonium groups, a high proportion of which are in the salt form when the polymer is dry but which undergo dissociation and salvation upon contact with bodily fluid. In the dissociated state, the polymer chain will have a series of functional groups attached to it which groups have the same electric charge (e.g., —NH3+ +H3N—) and thus repel one another. This leads to expansion of the polymer structure, which, in turn permits further absorption of negatively charged odorous molecules and thus the control thereof.
Secondly, the positively charged cationic groups of the chitosan materials will interact with negatively charged anionic groups-bearing molecules present in bodily fluids, like the carboxylic groups of proteins or hydroxylic acid bearing entities like short chain acid (e.g., butyric acid). This will result in the formation of tri-dimensional net between chitosan materials and such molecules with anionic groups (gelification of the bodily fluids). This gelification will entrap most odorous molecules (like lipids, acids) thereby controlling malodor.
Thirdly and more importantly the chitosan materials are believed to act as antimicrobial agents. Indeed the chitosan materials with their positively charged cationic groups will interfere with negatively charged surface of microorganism walls, thereby inhibiting the growth of such microorganisms or even killing such microorganisms. These chitosan materials will also interfere with negatively charged surface of enzymes, thereby inactivating the enzymatic activity, which, like the microbial activity, are otherwise responsible for the formation of malodorous components. The chitosan materials further act by their indirect antimicrobial activity by linking some of the microorganism nutriments like lipids and/or minerals.
In a preferred embodiment of the present invention the chitosan materials used are chitosan salts. Without to be bound by theory it is speculated that chitosan salts, due to a higher percentage of positively charged cationic groups, delivers all above mentioned benefits immediately upon contact with bodily fluids.
Advantageously the presence of the anionic absorbent gelling material boosts the odor controlling properties of chitosan materials. More generally, the anionic absorbent gelling materials increase the cationic properties of chitosan materials which result in enhanced antimicrobial activity, enhanced absorption activity and enhanced gelification properties. Without to be bound by any theory it is believed that the carboxylic groups of the absorbent gelling materials protonate the amino groups of the chitosan materials, enhancing thereby the numbers of positively charged ammonium groups (—NH3+) of the chitosan materials and thus the cationic character of the chitosan materials.
The use of chitosan materials together with anionic absorbent gelling materials, preferably synthetic absorbent gelling materials, in absorbent articles also provides improved body fluid absorbing performance not only towards water but especially towards electrolyte-containing fluids. More generally, this combination, when used in absorbent articles, provides enhanced fluid handling properties, i.e., not only improved absorption performance towards water and especially towards electrolytes-containing fluids, this even under pressure conditions, but also reduced wetting through (i.e., reduced fluid leakage) and reduced rewetting of the topsheet.
In a preferred embodiment of the present invention the article comprises chitosan salts, preferably water-soluble chitosan salts, together with anionic absorbent gelling material, preferably having a degree of neutralization of 50% to 90%, to provide both optimum odor control properties and fluid handling properties. Advantageously, these properties are delivered immediately upon exposure of the article to bodily fluids and last for a prolonged wearing time of the article by the user. Without the intention to be bound by any theory it is speculated that these benefits are due to the availability of higher percentages of positively charged cationic groups of the chitosan salt upon contact with bodily fluids (compared for example to chitosan base material) as well as to the properties of the absorbent gelling material to further increase the percentage of positively charged groups of the chitosan salt, thereby maintaining all previously mentioned benefits upon a prolonged wearing time of the article.
The present invention is preferably directed to disposable absorbent articles like pantiliners, feminine napkins, incontinent pads, diapers, tampons, interlabial pads, perspiration pads, surgical pads, breast pads, human or animal waste management devices and the like. Other articles suitable for use according to the present invention further include articles designed to be placed against or in proximity to the body such as clothing, bandages, thermal pads, acne pads, cold pads, compresses, surgical pads/dressings and the like, body cleansing articles like impregnated wipes/tissues (e.g. baby wipes, wipes for feminine intimate hygiene), articles for absorbing perspiration such as shoe insoles, shirt inserts, and the like, and articles for animals like litters and the like.